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Singhal A, Roth C, Micheva-Viteva SN, Venu V, Lappala A, Lee JT, Starkenburg SR, Steadman CR, Sanbonmatsu KY. Human Coronavirus Infection Reorganizes Spatial Genomic Architecture in Permissive Lung Cells. RESEARCH SQUARE 2024:rs.3.rs-3979539. [PMID: 38559036 PMCID: PMC10980144 DOI: 10.21203/rs.3.rs-3979539/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Chromatin conformation capture followed by next-generation sequencing in combination with large-scale polymer simulations (4DHiC) produces detailed information on genomic loci interactions, allowing for the interrogation of 3D spatial genomic structures. Here, Hi-C data was acquired from the infection of fetal lung fibroblast (MRC5) cells with α-coronavirus 229E (CoV229E). Experimental Hi-C contact maps were used to determine viral-induced changes in genomic architecture over a 48-hour time period following viral infection, revealing substantial alterations in contacts within chromosomes and in contacts between different chromosomes. To gain further structural insight and quantify the underlying changes, we applied the 4DHiC polymer simulation method to reconstruct the 3D genomic structures and dynamics corresponding to the Hi-C maps. The models successfully reproduced experimental Hi-C data, including the changes in contacts induced by viral infection. Our 3D spatial simulations uncovered widespread chromatin restructuring, including increased chromosome compactness and A-B compartment mixing arising from infection. Our model also suggests increased spatial accessibility to regions containing interferon-stimulated genes upon infection with CoV229E, followed by chromatin restructuring at later time points, potentially inducing the migration of chromatin into more compact regions. This is consistent with previously observed suppression of gene expression. Our spatial genomics study provides a mechanistic structural basis for changes in chromosome architecture induced by coronavirus infection in lung cells.
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Affiliation(s)
- Ankush Singhal
- Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos,NM, USA
| | - Cullen Roth
- Genomics and Bioanalytics, Los Alamos National Laboratory, Los Alamos, NM, USA
| | | | - Vrinda Venu
- Climate, Ecology & Environment, Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Anna Lappala
- Department of Genetics, The Blavatnik Institute, Harvard Medical School, Boston, USA
| | - Jeannie T. Lee
- Department of Genetics, The Blavatnik Institute, Harvard Medical School, Boston, USA
- Departement of Molecular Biology, Massachusetts General Hospital, Boston, USA
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2
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Krueger K, Lamenza F, Gu H, El-Hodiri H, Wester J, Oberdick J, Fischer AJ, Oghumu S. Sex differences in susceptibility to substance use disorder: Role for X chromosome inactivation and escape? Mol Cell Neurosci 2023; 125:103859. [PMID: 37207894 PMCID: PMC10286730 DOI: 10.1016/j.mcn.2023.103859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 05/01/2023] [Accepted: 05/08/2023] [Indexed: 05/21/2023] Open
Abstract
There is a sex-based disparity associated with substance use disorders (SUDs) as demonstrated by clinical and preclinical studies. Females are known to escalate from initial drug use to compulsive drug-taking behavior (telescoping) more rapidly, and experience greater negative withdrawal effects than males. Although these biological differences have largely been attributed to sex hormones, there is evidence for non-hormonal factors, such as the influence of the sex chromosome, which underlie sex disparities in addiction behavior. However, genetic and epigenetic mechanisms underlying sex chromosome influences on substance abuse behavior are not completely understood. In this review, we discuss the role that escape from X-chromosome inactivation (XCI) in females plays in sex-associated differences in addiction behavior. Females have two X chromosomes (XX), and during XCI, one X chromosome is randomly chosen to be transcriptionally silenced. However, some X-linked genes escape XCI and display biallelic gene expression. We generated a mouse model using an X-linked gene specific bicistronic dual reporter mouse as a tool to visualize allelic usage and measure XCI escape in a cell specific manner. Our results revealed a previously undiscovered X-linked gene XCI escaper (CXCR3), which is variable and cell type dependent. This illustrates the highly complex and context dependent nature of XCI escape which is largely understudied in the context of SUD. Novel approaches such as single cell RNA sequencing will provide a global molecular landscape and impact of XCI escape in addiction and facilitate our understanding of the contribution of XCI escape to sex disparities in SUD.
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Affiliation(s)
- Kate Krueger
- Department of Pharmacy, The Ohio State University, Columbus, OH, USA
| | - Felipe Lamenza
- Department of Pathology, The Ohio State University Wexner Medical Center, Columbus, OH, USA; Department of Microbiology, The Ohio State University, Columbus, OH, USA
| | - Howard Gu
- Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH, USA
| | - Heithem El-Hodiri
- Department of Neuroscience, The Ohio State University, Columbus, OH, USA
| | - Jason Wester
- Department of Neuroscience, The Ohio State University, Columbus, OH, USA
| | - John Oberdick
- Department of Neuroscience, The Ohio State University, Columbus, OH, USA
| | - Andy J Fischer
- Department of Neuroscience, The Ohio State University, Columbus, OH, USA
| | - Steve Oghumu
- Department of Pathology, The Ohio State University Wexner Medical Center, Columbus, OH, USA.
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3
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Wistuba J, Beumer C, Brehm R, Gromoll J. 41,XX Y * male mice: An animal model for Klinefelter syndrome. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2020; 184:267-278. [PMID: 32432406 DOI: 10.1002/ajmg.c.31796] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Revised: 04/28/2020] [Accepted: 04/29/2020] [Indexed: 12/25/2022]
Abstract
Klinefelter syndrome (KS, 47,XXY) is the most frequent male chromosomal aneuploidy resulting in a highly heterogeneous clinical phenotype associated with hormonal dysbalance, increased rate of co-morbidities, and reduced lifespan. Two hallmarks of KS-affecting testicular functions are consistently observed: Hypergonadotropic hypogonadism and germ cell (GC) loss resulting in infertility. Although KS is being studied for decades, the underlying mechanisms for the observed pathophysiology are still unclear. Due to ethical restrictions, studies in humans are limited, and consequently, suitable animal models are needed to address the consequences of a supernumerary X chromosome. Mouse strains with comparable aneuploidies have been generated and yielded highly relevant insights into KS. We briefly describe the establishment of the KS mouse models, summarize the knowledge gained by their use, compare findings from the mouse models to those obtained in clinical studies, and also reflect on limitations of the currently used models derived from the B6Ei.Lt-Y* mouse strain, in which the Y chromosome is altered and its centromere position changed into a more distal location provoking meiotic non-disjunction. Breeding such as XY* males to XX females, the target 41,XXY *, and 41,XXY males are generated. Here, we summarize features of both models but report in particular findings from our 41,XXY * mice including some novel data on Sertoli cell characteristics.
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Affiliation(s)
- Joachim Wistuba
- Institute of Reproductive and Regenerative Biology, Centre of Reproductive Medicine and Andrology, University of Münster, Münster, Germany
| | - Cristin Beumer
- Institute of Reproductive and Regenerative Biology, Centre of Reproductive Medicine and Andrology, University of Münster, Münster, Germany
| | - Ralph Brehm
- Functional Histology and Cell Biology, Institute for Anatomy, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany
| | - Jörg Gromoll
- Institute of Reproductive and Regenerative Biology, Centre of Reproductive Medicine and Andrology, University of Münster, Münster, Germany
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4
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Santos-Rebouças CB, Boy R, Vianna EQ, Gonçalves AP, Piergiorge RM, Abdala BB, Dos Santos JM, Calassara V, Machado FB, Medina-Acosta E, Pimentel MMG. Skewed X-Chromosome Inactivation and Compensatory Upregulation of Escape Genes Precludes Major Clinical Symptoms in a Female With a Large Xq Deletion. Front Genet 2020; 11:101. [PMID: 32194616 PMCID: PMC7064548 DOI: 10.3389/fgene.2020.00101] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 01/29/2020] [Indexed: 11/13/2022] Open
Abstract
In mammalian females, X-chromosome inactivation (XCI) acts as a dosage compensation mechanism that equalizes X-linked genes expression between homo- and heterogametic sexes. However, approximately 12–23% of X-linked genes escape from XCI, being bi-allelic expressed. Herein, we report on genetic and functional data from an asymptomatic female of a Fragile X syndrome family, who harbors a large deletion on the X-chromosome. Array-CGH uncovered that the de novo, terminal, paternally originated 32 Mb deletion on Xq25-q28 spans 598 RefSeq genes, including escape and variable escape genes. Androgen receptor (AR) and retinitis pigmentosa 2 (RP2) methylation assays showed extreme skewed XCI ratios from both peripheral blood and buccal mucosa, silencing the abnormal X-chromosome. Surprisingly, transcriptome-wide analysis revealed that escape and variable escape genes spanning the deletion are mostly upregulated on the active X-chromosome, precluding major clinical/cognitive phenotypes in the female. Metaphase high count, hemizygosity concordance for microsatellite markers, and monoallelic expression of genes within the deletion suggest the absence of mosaicism in both blood and buccal mucosa. Taken together, our data suggest that an additional protective gene-by-gene mechanism occurs at the transcriptional level in the active X-chromosome to counterbalance detrimental phenotype effects of large Xq deletions.
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Affiliation(s)
- Cíntia B Santos-Rebouças
- Department of Genetics, Institute of Biology Roberto Alcantara Gomes, State University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Raquel Boy
- Pedro Ernesto University Hospital, State University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Evelyn Q Vianna
- Department of Genetics, Institute of Biology Roberto Alcantara Gomes, State University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Andressa P Gonçalves
- Department of Genetics, Institute of Biology Roberto Alcantara Gomes, State University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Rafael M Piergiorge
- Department of Genetics, Institute of Biology Roberto Alcantara Gomes, State University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Bianca B Abdala
- Department of Genetics, Institute of Biology Roberto Alcantara Gomes, State University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Jussara M Dos Santos
- Department of Genetics, Institute of Biology Roberto Alcantara Gomes, State University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Veluma Calassara
- Department of Genetics, Institute of Biology Roberto Alcantara Gomes, State University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Filipe B Machado
- Department of Biological Sciences, Minas Gerais State University, Ubá, Brazil
| | - Enrique Medina-Acosta
- Laboratory of Biotechnology, State University of Northern Rio de Janeiro Darcy Ribeiro, Rio de Janeiro, Brazil
| | - Márcia M G Pimentel
- Department of Genetics, Institute of Biology Roberto Alcantara Gomes, State University of Rio de Janeiro, Rio de Janeiro, Brazil
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5
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Fang H, Disteche CM, Berletch JB. X Inactivation and Escape: Epigenetic and Structural Features. Front Cell Dev Biol 2019; 7:219. [PMID: 31632970 PMCID: PMC6779695 DOI: 10.3389/fcell.2019.00219] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 09/18/2019] [Indexed: 12/27/2022] Open
Abstract
X inactivation represents a complex multi-layer epigenetic mechanism that profoundly modifies chromatin composition and structure of one X chromosome in females. The heterochromatic inactive X chromosome adopts a unique 3D bipartite structure and a location close to the nuclear periphery or the nucleolus. X-linked lncRNA loci and their transcripts play important roles in the recruitment of proteins that catalyze chromatin and DNA modifications for silencing, as well as in the control of chromatin condensation and location of the inactive X chromosome. A subset of genes escapes X inactivation, raising questions about mechanisms that preserve their expression despite being embedded within heterochromatin. Escape gene expression differs between males and females, which can lead to physiological sex differences. We review recent studies that emphasize challenges in understanding the role of lncRNAs in the control of epigenetic modifications, structural features and nuclear positioning of the inactive X chromosome. Second, we highlight new findings about the distribution of genes that escape X inactivation based on single cell studies, and discuss the roles of escape genes in eliciting sex differences in health and disease.
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Affiliation(s)
- He Fang
- Department of Pathology, University of Washington, Seattle, WA, United States
| | - Christine M. Disteche
- Department of Pathology, University of Washington, Seattle, WA, United States
- Department of Medicine, University of Washington, Seattle, WA, United States
| | - Joel B. Berletch
- Department of Pathology, University of Washington, Seattle, WA, United States
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Jackson MR, Loring KE, Homan CC, Thai MH, Määttänen L, Arvio M, Jarvela I, Shaw M, Gardner A, Gecz J, Shoubridge C. Heterozygous loss of function of IQSEC2/ Iqsec2 leads to increased activated Arf6 and severe neurocognitive seizure phenotype in females. Life Sci Alliance 2019; 2:2/4/e201900386. [PMID: 31439632 PMCID: PMC6706959 DOI: 10.26508/lsa.201900386] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 07/25/2019] [Accepted: 08/15/2019] [Indexed: 12/30/2022] Open
Abstract
Clinical presentations of mutations in the IQSEC2 gene on the X-chromosome initially implicated to cause non-syndromic intellectual disability (ID) in males have expanded to include early onset seizures in males as well as in females. The molecular pathogenesis is not well understood, nor the mechanisms driving disease expression in heterozygous females. Using a CRISPR/Cas9-edited Iqsec2 KO mouse model, we confirm the loss of Iqsec2 mRNA expression and lack of Iqsec2 protein within the brain of both founder and progeny mice. Both male (52%) and female (46%) Iqsec2 KO mice present with frequent and recurrent seizures. Focusing on Iqsec2 KO heterozygous female mice, we demonstrate increased hyperactivity, altered anxiety and fear responses, decreased social interactions, delayed learning capacity and decreased memory retention/novel recognition, recapitulating psychiatric issues, autistic-like features, and cognitive deficits present in female patients with loss-of-function IQSEC2 variants. Despite Iqsec2 normally acting to activate Arf6 substrate, we demonstrate that mice modelling the loss of Iqsec2 function present with increased levels of activated Arf6. We contend that loss of Iqsec2 function leads to altered regulation of activated Arf6-mediated responses to synaptic signalling and immature synaptic networks. We highlight the importance of IQSEC2 function for females by reporting a novel nonsense variant c.566C > A, p.(S189*) in an elderly female patient with profound intellectual disability, generalised seizures, and behavioural disturbances. Our human and mouse data reaffirm IQSEC2 as another disease gene with an unexpected X-chromosome heterozygous female phenotype. Our Iqsec2 mouse model recapitulates the phenotypes observed in human patients despite the differences in the IQSEC2/Iqsec2 gene X-chromosome inactivation between the species.
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Affiliation(s)
- Matilda R Jackson
- Intellectual Disability Research, Adelaide Medical School, The University of Adelaide, Adelaide, Australia.,Department of Paediatrics, Robinson Research Institute, University of Adelaide, Adelaide, Australia
| | - Karagh E Loring
- Intellectual Disability Research, Adelaide Medical School, The University of Adelaide, Adelaide, Australia.,Department of Paediatrics, Robinson Research Institute, University of Adelaide, Adelaide, Australia
| | - Claire C Homan
- Department of Paediatrics, Robinson Research Institute, University of Adelaide, Adelaide, Australia
| | - Monica Hn Thai
- Intellectual Disability Research, Adelaide Medical School, The University of Adelaide, Adelaide, Australia
| | - Laura Määttänen
- Department of Child Neurology, Turku University Hospital, Turku, Finland
| | - Maria Arvio
- Department of Child Neurology, Turku University Hospital, Turku, Finland.,Joint Authority for Päijät-Häme Social and Health Care, Lahti, Finland.,PEDEGO, Oulu University Hospital, Oulu, Finland
| | - Irma Jarvela
- Department of Medical Genetics, University of Helsinki, Helsinki, Finland
| | - Marie Shaw
- Department of Paediatrics, Robinson Research Institute, University of Adelaide, Adelaide, Australia
| | - Alison Gardner
- Department of Paediatrics, Robinson Research Institute, University of Adelaide, Adelaide, Australia
| | - Jozef Gecz
- Department of Paediatrics, Robinson Research Institute, University of Adelaide, Adelaide, Australia.,South Australian Health and Medical Research Institute, Adelaide, Australia
| | - Cheryl Shoubridge
- Intellectual Disability Research, Adelaide Medical School, The University of Adelaide, Adelaide, Australia .,Department of Paediatrics, Robinson Research Institute, University of Adelaide, Adelaide, Australia
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7
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Peeters SB, Korecki AJ, Simpson EM, Brown CJ. Human cis-acting elements regulating escape from X-chromosome inactivation function in mouse. Hum Mol Genet 2019; 27:1252-1262. [PMID: 29401310 PMCID: PMC6159535 DOI: 10.1093/hmg/ddy039] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Accepted: 01/29/2018] [Indexed: 12/18/2022] Open
Abstract
A long-standing question concerning X-chromosome inactivation (XCI) has been how some genes avoid the otherwise stable chromosome-wide heterochromatinization of the inactive X chromosome. As 20% or more of human X-linked genes escape from inactivation, such genes are an important contributor to sex differences in gene expression. Although both human and mouse have genes that escape from XCI, more genes escape in humans than mice, with human escape genes often clustering in larger domains than the single escape genes of mouse. Mouse models offer a well-characterized and readily manipulated system in which to study XCI, but given the differences in genes that escape it is unclear whether the mechanism of escape gene regulation is conserved. To address conservation of the process and the potential to identify elements by modelling human escape gene regulation using mouse, we integrated a human and a mouse BAC each containing an escape gene and flanking subject genes at the mouse X-linked Hprt gene. Escape-level expression and corresponding low promoter DNA methylation of human genes RPS4X and CITED1 demonstrated that the mouse system is capable of recognizing human elements and therefore can be used as a model for further refinement of critical elements necessary for escape from XCI in humans.
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Affiliation(s)
- Samantha B Peeters
- Department of Medical Genetics, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Andrea J Korecki
- Centre for Molecular Medicine and Therapeutics at British Columbia Children's Hospital, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Elizabeth M Simpson
- Centre for Molecular Medicine and Therapeutics at British Columbia Children's Hospital, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Carolyn J Brown
- Department of Medical Genetics, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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8
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Gonadal mosaicism of a novel IQSEC2 variant causing female limited intellectual disability and epilepsy. Eur J Hum Genet 2017; 25:763-767. [PMID: 28295038 DOI: 10.1038/ejhg.2017.29] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 01/23/2017] [Accepted: 02/07/2017] [Indexed: 02/01/2023] Open
Abstract
We report a family with four girls with moderate to severe intellectual disability and epilepsy. Two girls showed regression in adolescence and died of presumed sudden unexpected death in epilepsy at 16 and 22 years. Whole exome sequencing identified a truncating pathogenic variant in IQSEC2 at NM_001111125.2: c.2679_2680insA, p.(D894fs*10), a recently identified cause of epileptic encephalopathy in females (MIM 300522). The IQSEC2 variant was identified in both surviving affected sisters but in neither parent. We describe the phenotypic spectrum associated with IQSEC2 variants, highlighting how IQSEC2 is adding to a growing list of X-linked genes that have a female-specific phenotype typically associated with de novo mutations. This report illustrates the need for careful review of all whole exome data, incorporating all possible modes of inheritance including that suggested by the family history.
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Zerem A, Haginoya K, Lev D, Blumkin L, Kivity S, Linder I, Shoubridge C, Palmer EE, Field M, Boyle J, Chitayat D, Gaillard WD, Kossoff EH, Willems M, Geneviève D, Tran-Mau-Them F, Epstein O, Heyman E, Dugan S, Masurel-Paulet A, Piton A, Kleefstra T, Pfundt R, Sato R, Tzschach A, Matsumoto N, Saitsu H, Leshinsky-Silver E, Lerman-Sagie T. The molecular and phenotypic spectrum ofIQSEC2-related epilepsy. Epilepsia 2016; 57:1858-1869. [DOI: 10.1111/epi.13560] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/15/2016] [Indexed: 01/21/2023]
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10
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Marks H, Kerstens HHD, Barakat TS, Splinter E, Dirks RAM, van Mierlo G, Joshi O, Wang SY, Babak T, Albers CA, Kalkan T, Smith A, Jouneau A, de Laat W, Gribnau J, Stunnenberg HG. Dynamics of gene silencing during X inactivation using allele-specific RNA-seq. Genome Biol 2015; 16:149. [PMID: 26235224 PMCID: PMC4546214 DOI: 10.1186/s13059-015-0698-x] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 06/18/2015] [Indexed: 02/02/2023] Open
Abstract
BACKGROUND During early embryonic development, one of the two X chromosomes in mammalian female cells is inactivated to compensate for a potential imbalance in transcript levels with male cells, which contain a single X chromosome. Here, we use mouse female embryonic stem cells (ESCs) with non-random X chromosome inactivation (XCI) and polymorphic X chromosomes to study the dynamics of gene silencing over the inactive X chromosome by high-resolution allele-specific RNA-seq. RESULTS Induction of XCI by differentiation of female ESCs shows that genes proximal to the X-inactivation center are silenced earlier than distal genes, while lowly expressed genes show faster XCI dynamics than highly expressed genes. The active X chromosome shows a minor but significant increase in gene activity during differentiation, resulting in complete dosage compensation in differentiated cell types. Genes escaping XCI show little or no silencing during early propagation of XCI. Allele-specific RNA-seq of neural progenitor cells generated from the female ESCs identifies three regions distal to the X-inactivation center that escape XCI. These regions, which stably escape during propagation and maintenance of XCI, coincide with topologically associating domains (TADs) as present in the female ESCs. Also, the previously characterized gene clusters escaping XCI in human fibroblasts correlate with TADs. CONCLUSIONS The gene silencing observed during XCI provides further insight in the establishment of the repressive complex formed by the inactive X chromosome. The association of escape regions with TADs, in mouse and human, suggests that TADs are the primary targets during propagation of XCI over the X chromosome.
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Affiliation(s)
- Hendrik Marks
- Radboud University, Faculty of Science, Department of Molecular Biology, Radboud Institute for Molecular Life Sciences (RIMLS), 6500HB, Nijmegen, The Netherlands.
| | - Hindrik H D Kerstens
- Radboud University, Faculty of Science, Department of Molecular Biology, Radboud Institute for Molecular Life Sciences (RIMLS), 6500HB, Nijmegen, The Netherlands.
| | - Tahsin Stefan Barakat
- Department of Reproduction and Development, Erasmus MC, University Medical Center, Rotterdam, The Netherlands.
| | - Erik Splinter
- Hubrecht Institute, University Medical Center Utrecht, Uppsalalaan 8, 3584CT, Utrecht, The Netherlands.
| | - René A M Dirks
- Radboud University, Faculty of Science, Department of Molecular Biology, Radboud Institute for Molecular Life Sciences (RIMLS), 6500HB, Nijmegen, The Netherlands.
| | - Guido van Mierlo
- Radboud University, Faculty of Science, Department of Molecular Biology, Radboud Institute for Molecular Life Sciences (RIMLS), 6500HB, Nijmegen, The Netherlands.
| | - Onkar Joshi
- Radboud University, Faculty of Science, Department of Molecular Biology, Radboud Institute for Molecular Life Sciences (RIMLS), 6500HB, Nijmegen, The Netherlands.
| | - Shuang-Yin Wang
- Radboud University, Faculty of Science, Department of Molecular Biology, Radboud Institute for Molecular Life Sciences (RIMLS), 6500HB, Nijmegen, The Netherlands.
| | - Tomas Babak
- Biology Department, Queen's University, Kingston, ON, Canada.
| | - Cornelis A Albers
- Radboud University, Faculty of Science, Department of Molecular Developmental Biology, Radboud Institute for Molecular Life Sciences (RIMLS), 6500HB, Nijmegen, The Netherlands.
| | - Tüzer Kalkan
- Wellcome Trust-Medical Research Council Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QR, UK.
| | - Austin Smith
- Wellcome Trust-Medical Research Council Stem Cell Institute, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QR, UK.
| | - Alice Jouneau
- INRA, UMR1198 Biologie du Développement et Reproduction, F-78350, Jouy-en-Josas, France.
| | - Wouter de Laat
- Hubrecht Institute, University Medical Center Utrecht, Uppsalalaan 8, 3584CT, Utrecht, The Netherlands.
| | - Joost Gribnau
- Department of Reproduction and Development, Erasmus MC, University Medical Center, Rotterdam, The Netherlands.
| | - Hendrik G Stunnenberg
- Radboud University, Faculty of Science, Department of Molecular Biology, Radboud Institute for Molecular Life Sciences (RIMLS), 6500HB, Nijmegen, The Netherlands.
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Xp11.2 microduplications including IQSEC2, TSPYL2 and KDM5C genes in patients with neurodevelopmental disorders. Eur J Hum Genet 2015; 24:373-80. [PMID: 26059843 DOI: 10.1038/ejhg.2015.123] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Revised: 03/26/2015] [Accepted: 05/06/2015] [Indexed: 01/06/2023] Open
Abstract
Copy number variations are a common cause of intellectual disability (ID). Determining the contribution of copy number variants (CNVs), particularly gains, to disease remains challenging. Here, we report four males with ID with sub-microscopic duplications at Xp11.2 and review the few cases with overlapping duplications reported to date. We established the extent of the duplicated regions in each case encompassing a minimum of three known disease genes TSPYL2, KDM5C and IQSEC2 with one case also duplicating the known disease gene HUWE1. Patients with a duplication encompassing TSPYL2, KDM5C and IQSEC2 without gains of nearby SMC1A and HUWE1 genes have not been reported thus far. All cases presented with ID and significant deficits of speech development. Some patients also manifested behavioral disturbances such as hyperactivity and attention-deficit/hyperactivity disorder. Lymphoblastic cell lines from patients show markedly elevated levels of TSPYL2, KDM5C and SMC1A, transcripts consistent with the extent of their CNVs. The duplicated region in our patients contains several genes known to escape X-inactivation, including KDM5C, IQSEC2 and SMC1A. In silico analysis of expression data in selected gene expression omnibus series indicates that dosage of these genes, especially IQSEC2, is similar in males and females despite the fact they escape from X-inactivation in females. Taken together, the data suggest that gains in Xp11.22 including IQSEC2 cause ID and are associated with hyperactivity and attention-deficit/hyperactivity disorder, and are likely to be dosage-sensitive in males.
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12
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Olson HE, Tambunan D, LaCoursiere C, Goldenberg M, Pinsky R, Martin E, Ho E, Khwaja O, Kaufmann WE, Poduri A. Mutations in epilepsy and intellectual disability genes in patients with features of Rett syndrome. Am J Med Genet A 2015; 167A:2017-25. [PMID: 25914188 DOI: 10.1002/ajmg.a.37132] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 04/12/2015] [Indexed: 11/09/2022]
Abstract
Rett syndrome and neurodevelopmental disorders with features overlapping this syndrome frequently remain unexplained in patients without clinically identified MECP2 mutations. We recruited a cohort of 11 patients with features of Rett syndrome and negative initial clinical testing for mutations in MECP2. We analyzed their phenotypes to determine whether patients met formal criteria for Rett syndrome, reviewed repeat clinical genetic testing, and performed exome sequencing of the probands. Using 2010 diagnostic criteria, three patients had classical Rett syndrome, including two for whom repeat MECP2 gene testing had identified mutations. In a patient with neonatal onset epilepsy with atypical Rett syndrome, we identified a frameshift deletion in STXBP1. Among seven patients with features of Rett syndrome not fulfilling formal diagnostic criteria, four had suspected pathogenic mutations, one each in MECP2, FOXG1, SCN8A, and IQSEC2. MECP2 mutations are highly correlated with classical Rett syndrome. Genes associated with atypical Rett syndrome, epilepsy, or intellectual disability should be considered in patients with features overlapping with Rett syndrome and negative MECP2 testing. While most of the identified mutations were apparently de novo, the SCN8A variant was inherited from an unaffected parent mosaic for the mutation, which is important to note for counseling regarding recurrence risks.
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Affiliation(s)
- Heather E Olson
- Epilepsy Genetics Program, Division of Epilepsy & Clinical Neurophysiology, Boston Children's Hospital, Boston, Massachusetts.,Harvard Medical School, Boston, Massachusetts.,Neurogenetics Program, Boston Children's Hospital, Boston, Massachusetts.,Department of Neurology, Boston Children's Hospital, Boston, Massachusetts
| | - Dimira Tambunan
- Epilepsy Genetics Program, Division of Epilepsy & Clinical Neurophysiology, Boston Children's Hospital, Boston, Massachusetts
| | - Christopher LaCoursiere
- Epilepsy Genetics Program, Division of Epilepsy & Clinical Neurophysiology, Boston Children's Hospital, Boston, Massachusetts
| | - Marti Goldenberg
- Department of Neurology, Boston Children's Hospital, Boston, Massachusetts
| | - Rebecca Pinsky
- Epilepsy Genetics Program, Division of Epilepsy & Clinical Neurophysiology, Boston Children's Hospital, Boston, Massachusetts
| | - Emilie Martin
- Epilepsy Genetics Program, Division of Epilepsy & Clinical Neurophysiology, Boston Children's Hospital, Boston, Massachusetts
| | - Eugenia Ho
- Department of Neurology, Boston Children's Hospital, Boston, Massachusetts.,Rett Syndrome Program, Boston Children's Hospital, Boston, Massachusetts
| | - Omar Khwaja
- Neurogenetics Program, Boston Children's Hospital, Boston, Massachusetts.,Department of Neurology, Boston Children's Hospital, Boston, Massachusetts.,Rett Syndrome Program, Boston Children's Hospital, Boston, Massachusetts
| | - Walter E Kaufmann
- Harvard Medical School, Boston, Massachusetts.,Neurogenetics Program, Boston Children's Hospital, Boston, Massachusetts.,Department of Neurology, Boston Children's Hospital, Boston, Massachusetts.,Rett Syndrome Program, Boston Children's Hospital, Boston, Massachusetts
| | - Annapurna Poduri
- Epilepsy Genetics Program, Division of Epilepsy & Clinical Neurophysiology, Boston Children's Hospital, Boston, Massachusetts.,Harvard Medical School, Boston, Massachusetts.,Neurogenetics Program, Boston Children's Hospital, Boston, Massachusetts.,Department of Neurology, Boston Children's Hospital, Boston, Massachusetts.,F. M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, Massachusetts
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13
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Nizon M, Andrieux J, Rooryck C, de Blois MC, Bourel-Ponchel E, Bourgois B, Boute O, David A, Delobel B, Duban-Bedu B, Giuliano F, Goldenberg A, Grotto S, Héron D, Karmous-Benailly H, Keren B, Lacombe D, Lapierre JM, Le Caignec C, Le Galloudec E, Le Merrer M, Le Moing AG, Mathieu-Dramard M, Nusbaum S, Pichon O, Pinson L, Raoul O, Rio M, Romana S, Roubertie A, Colleaux L, Turleau C, Vekemans M, Nabbout R, Malan V. Phenotype-genotype correlations in 17 new patients with an Xp11.23p11.22 microduplication and review of the literature. Am J Med Genet A 2014; 167A:111-22. [PMID: 25425167 DOI: 10.1002/ajmg.a.36807] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2014] [Accepted: 09/04/2014] [Indexed: 11/12/2022]
Abstract
Array comparative genomic hybridization (array CGH) has proven its utility in uncovering cryptic rearrangements in patients with X-linked intellectual disability. In 2009, Giorda et al. identified inherited and de novo recurrent Xp11.23p11.22 microduplications in two males and six females from a wide cohort of patients presenting with syndromic intellectual disability. To date, 14 females and 5 males with an overlapping microduplication have been reported in the literature. To further characterize this emerging syndrome, we collected clinical and microarray data from 17 new patients, 10 females, and 7 males. The Xp11.23p11.2 microduplications detected by array CGH ranged in size from 331 Kb to 8.9 Mb. Five patients harbored 4.5 Mb recurrent duplications mediated by non-allelic homologous recombination between segmental duplications and 12 harbored atypical duplications. The chromosomal rearrangement occurred de novo in eight patients and was inherited in six affected males from three families. Patients shared several common major characteristics including moderate to severe intellectual disability, early onset of puberty, language impairment, and age related epileptic syndromes such as West syndrome and focal epilepsy with activation during sleep evolving in some patients to continuous spikes-and-waves during slow sleep. Atypical microduplications allowed us to identify minimal critical regions that might be responsible for specific clinical findings of the syndrome and to suggest possible candidate genes: FTSJ1 and SHROOM4 for intellectual disability along with PQBP1 and SLC35A2 for epilepsy. Xp11.23p11.22 microduplication is a recently-recognized syndrome associated with intellectual disability, epilepsy, and early onset of puberty in females. In this study, we propose several genes that could contribute to the phenotype.
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Affiliation(s)
- Mathilde Nizon
- Département de Génétique, Université Paris Descartes, Sorbonne Paris Cité, Institut IMAGINE UMR_S1163, Hôpital Necker-Enfants Malades, Paris, France
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14
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Merzouk S, Deuve JL, Dubois A, Navarro P, Avner P, Morey C. Lineage-specific regulation of imprinted X inactivation in extraembryonic endoderm stem cells. Epigenetics Chromatin 2014; 7:11. [PMID: 25053977 PMCID: PMC4105886 DOI: 10.1186/1756-8935-7-11] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Accepted: 06/02/2014] [Indexed: 01/09/2023] Open
Abstract
Background Silencing of the paternal X chromosome (Xp), a phenomenon known as imprinted X-chromosome inactivation (I-XCI), characterises, amongst mouse extraembryonic lineages, the primitive endoderm and the extraembryonic endoderm (XEN) stem cells derived from it. Results Using a combination of chromatin immunoprecipitation characterisation of histone modifications and single-cell expression studies, we show that whilst the Xp in XEN cells, like the inactive X chromosome in other cell types, globally accumulates the repressive histone mark H3K27me3, a large number of Xp genes locally lack H3K27me3 and escape from I-XCI. In most cases this escape is specific to the XEN cell lineage. Importantly, the degree of escape and the genes concerned remain unchanged upon XEN conversion into visceral endoderm, suggesting stringent control of I-XCI in XEN derivatives. Surprisingly, chemical inhibition of EZH2, a member of the Polycomb repressive complex 2 (PRC2), and subsequent loss of H3K27me3 on the Xp, do not drastically perturb the pattern of silencing of Xp genes in XEN cells. Conclusions The observations that we report here suggest that the maintenance of gene expression profiles of the inactive Xp in XEN cells involves a tissue-specific mechanism that acts partly independently of PRC2 catalytic activity.
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Affiliation(s)
- Sarra Merzouk
- Mouse Molecular Genetics Laboratory, Pasteur Institute, 25 rue du Dr Roux, 75015 Paris, France ; Pasteur Cell, Pierre and Marie Curie University (UPMC), 25 rue du Dr Roux, 75015 Paris, France
| | - Jane Lynda Deuve
- Mouse Molecular Genetics Laboratory, Pasteur Institute, 25 rue du Dr Roux, 75015 Paris, France ; Present address: Pierre and Marie Curie University (UPMC), UMR7622, Institute of Biology of Paris-Seine (IBPS), 75005 Paris, France
| | - Agnès Dubois
- Mouse Molecular Genetics Laboratory, Pasteur Institute, 25 rue du Dr Roux, 75015 Paris, France ; Present address: Epigenetics of Stem Cells Laboratory', Pasteur Institute, 25 rue du Dr Roux, 75015 Paris, France
| | - Pablo Navarro
- Present address: Epigenetics of Stem Cells Laboratory', Pasteur Institute, 25 rue du Dr Roux, 75015 Paris, France
| | - Philip Avner
- Mouse Molecular Genetics Laboratory, Pasteur Institute, 25 rue du Dr Roux, 75015 Paris, France ; Present address: Dynamics of Epigenetic Regulation, EMBL Monterotondo, Adriano Buzzati-Traverso Campus, Via Ramarini 32, 00015 Monterotondo, Italy
| | - Céline Morey
- Mouse Molecular Genetics Laboratory, Pasteur Institute, 25 rue du Dr Roux, 75015 Paris, France
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Horvath LM, Li N, Carrel L. Deletion of an X-inactivation boundary disrupts adjacent gene silencing. PLoS Genet 2013; 9:e1003952. [PMID: 24278033 PMCID: PMC3836711 DOI: 10.1371/journal.pgen.1003952] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Accepted: 09/27/2013] [Indexed: 12/03/2022] Open
Abstract
In mammalian females, genes on one X are largely silenced by X-chromosome inactivation (XCI), although some “escape” XCI and are expressed from both Xs. Escapees can closely juxtapose X-inactivated genes and provide a tractable model for assessing boundary function at epigenetically regulated loci. To delimit sequences at an XCI boundary, we examined female mouse embryonic stem cells carrying X-linked BAC transgenes derived from an endogenous escape locus. Previously we determined that large BACs carrying escapee Kdm5c and flanking X-inactivated transcripts are properly regulated. Here we identify two lines with truncated BACs that partially and completely delete the distal Kdm5c XCI boundary. This boundary is not required for escape, since despite integrating into regions that are normally X inactivated, transgenic Kdm5c escapes XCI, as determined by RNA FISH and by structurally adopting an active conformation that facilitates long-range preferential association with other escapees. Yet, XCI regulation is disrupted in the transgene fully lacking the distal boundary; integration site genes up to 350 kb downstream of the transgene now inappropriately escape XCI. Altogether, these results reveal two genetically separable XCI regulatory activities at Kdm5c. XCI escape is driven by a dominant element(s) retained in the shortest transgene that therefore lies within or upstream of the Kdm5c locus. Additionally, the distal XCI boundary normally plays an essential role in preventing nearby genes from escaping XCI. Early in mammalian female development, one X chromosome is largely silenced to equalize X-linked gene expression between the sexes. Nevertheless, some genes “escape” this silencing and therefore are expressed from both X chromosomes. Understanding how these escape genes are regulated, particularly when they closely juxtapose silenced genes, may give important insight into regulatory transitions throughout the genome. To evaluate sequences that are essential for appropriate inactive X expression we analyzed large transgenes that integrated on the X chromosome in mouse embryonic stem cells. Transgenes that include an escape gene, Kdm5c, but lack all or part of the downstream sequences, including the X-inactivation boundary, still escape X inactivation. Nevertheless, downstream genes at the transgene insertion site are misregulated and now inappropriately escape X inactivation as well. These data identify two important regulatory activities at this locus. First, sequences retained within the truncated transgene are sufficient to direct the Kdm5c gene to escape X inactivation. Further, we have uncovered a function for an X-inactivation boundary in protecting adjacent genes from escape.
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Affiliation(s)
- Lindsay M. Horvath
- Department of Biochemistry and Molecular Biology, Pennsylvania State College of Medicine, Hershey, Pennsylvania, United States of America
| | - Nan Li
- Department of Biochemistry and Molecular Biology, Pennsylvania State College of Medicine, Hershey, Pennsylvania, United States of America
| | - Laura Carrel
- Department of Biochemistry and Molecular Biology, Pennsylvania State College of Medicine, Hershey, Pennsylvania, United States of America
- * E-mail:
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16
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Ibragimova I, Slifker MJ, Maradeo ME, Banumathy G, Dulaimi E, Uzzo RG, Cairns P. Genome-wide promoter methylome of small renal masses. PLoS One 2013; 8:e77309. [PMID: 24204800 PMCID: PMC3811999 DOI: 10.1371/journal.pone.0077309] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Accepted: 09/06/2013] [Indexed: 12/12/2022] Open
Abstract
The majority of renal cell carcinoma (RCC) is now incidentally detected and presents as small renal masses (SRMs) defined as ≤ 4 cm in size. SRMs are heterogeneous comprising several histological types of RCC each with different biology and behavior, and benign tumors mainly oncocytoma. The varied prognosis of the different types of renal tumor has implications for management options. A key epigenetic alteration involved in the initiation and progression of cancer is aberrant methylation in the promoter region of a gene. The hypermethylation is associated with transcriptional repression and is an important mechanism of inactivation of tumor suppressor genes in neoplastic cells. We have determined the genome-wide promoter methylation profiles of 47 pT1a and 2 pT1b clear cell, papillary or chromophobe RCC, 25 benign renal oncocytoma ≤ 4 cm and 4 normal renal parenchyma specimens by Infinium HumanMethylation27 beadchip technology. We identify gene promoter hypermethylation signatures that distinguish clear cell and papillary from each other, from chromophobe and oncocytoma, and from normal renal cells. Pairwise comparisons revealed genes aberrantly hypermethylated in a tumor type but unmethylated in normal, and often unmethylated in the other renal tumor types. About 0.4% to 1.7% of genes comprised the promoter methylome in SRMs. The Infinium methylation score for representative genes was verified by gold standard technologies. The genes identified as differentially methylated implicate pathways involved in metabolism, tissue response to injury, epithelial to mesenchymal transition (EMT), signal transduction and G-protein coupled receptors (GPCRs), cancer, and stem cell regulation in the biology of RCC. Our findings contribute towards an improved understanding of the development of RCC, the different biology and behavior of histological types, and discovery of molecular subtypes. The differential methylation signatures may have utility in early detection and particularly differential diagnosis for prognostic stratification as well as identify novel gene and pathway targets for therapeutic intervention.
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MESH Headings
- Adenoma, Oxyphilic/diagnosis
- Adenoma, Oxyphilic/genetics
- Adenoma, Oxyphilic/metabolism
- Aged
- Carcinoma, Renal Cell/diagnosis
- Carcinoma, Renal Cell/genetics
- Carcinoma, Renal Cell/metabolism
- Case-Control Studies
- DNA Methylation
- Diagnosis, Differential
- Epigenesis, Genetic
- Female
- Gene Expression Regulation, Neoplastic
- Genome, Human
- Humans
- Kidney/metabolism
- Kidney/pathology
- Kidney Neoplasms/diagnosis
- Kidney Neoplasms/genetics
- Kidney Neoplasms/metabolism
- Male
- Middle Aged
- Neoplasm Proteins/genetics
- Neoplasm Proteins/metabolism
- Promoter Regions, Genetic
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Affiliation(s)
- Ilsiya Ibragimova
- Cancer Epigenetics Program and Kidney Keystone Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, United States of America
| | - Michael J. Slifker
- Biostatistics and Bioinformatics, Fox Chase Cancer Center, Philadelphia, Pennsylvania, United States of America
| | - Marie E. Maradeo
- Cancer Epigenetics Program and Kidney Keystone Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, United States of America
| | - Gowrishankar Banumathy
- Cancer Epigenetics Program and Kidney Keystone Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, United States of America
| | - Essel Dulaimi
- Department of Pathology and Kidney Keystone Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, United States of America
| | - Robert G. Uzzo
- Department of Surgery and Kidney Keystone Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, United States of America
| | - Paul Cairns
- Cancer Epigenetics Program and Kidney Keystone Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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17
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Zhang Y, Castillo-Morales A, Jiang M, Zhu Y, Hu L, Urrutia AO, Kong X, Hurst LD. Genes that escape X-inactivation in humans have high intraspecific variability in expression, are associated with mental impairment but are not slow evolving. Mol Biol Evol 2013; 30:2588-601. [PMID: 24023392 PMCID: PMC3840307 DOI: 10.1093/molbev/mst148] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
In female mammals most X-linked genes are subject to X-inactivation. However, in humans some X-linked genes escape silencing, these escapees being candidates for the phenotypic aberrations seen in polyX karyotypes. These escape genes have been reported to be under stronger purifying selection than other X-linked genes. Although it is known that escape from X-inactivation is much more common in humans than in mice, systematic assays of escape in humans have to date employed only interspecies somatic cell hybrids. Here we provide the first systematic next-generation sequencing analysis of escape in a human cell line. We analyzed RNA and genotype sequencing data obtained from B lymphocyte cell lines derived from Europeans (CEU) and Yorubans (YRI). By replicated detection of heterozygosis in the transcriptome, we identified 114 escaping genes, including 76 not previously known to be escapees. The newly described escape genes cluster on the X chromosome in the same chromosomal regions as the previously known escapees. There is an excess of escaping genes associated with mental retardation, consistent with this being a common phenotype of polyX phenotypes. We find both differences between populations and between individuals in the propensity to escape. Indeed, we provide the first evidence for there being both hyper- and hypo-escapee females in the human population, consistent with the highly variable phenotypic presentation of polyX karyotypes. Considering also prior data, we reclassify genes as being always, never, and sometimes escape genes. We fail to replicate the prior claim that genes that escape X-inactivation are under stronger purifying selection than others.
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Affiliation(s)
- Yuchao Zhang
- State Key Laboratory of Medical Genomics, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, People's Republic of China
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18
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Ibragimova I, Maradeo ME, Dulaimi E, Cairns P. Aberrant promoter hypermethylation of PBRM1, BAP1, SETD2, KDM6A and other chromatin-modifying genes is absent or rare in clear cell RCC. Epigenetics 2013; 8:486-93. [PMID: 23644518 PMCID: PMC3741218 DOI: 10.4161/epi.24552] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Recent sequencing studies of clear cell (conventional) renal cell carcinoma (ccRCC) have identified inactivating point mutations in the chromatin-modifying genes PBRM1, KDM6A/UTX, KDM5C/JARID1C, SETD2, MLL2 and BAP1. To investigate whether aberrant hypermethylation is a mechanism of inactivation of these tumor suppressor genes in ccRCC, we sequenced the promoter region within a bona fide CpG island of PBRM1, KDM6A, SETD2 and BAP1 in bisulfite-modified DNA of a representative series of 50 primary ccRCC, 4 normal renal parenchyma specimens and 5 RCC cell lines. We also interrogated the promoter methylation status of KDM5C and ARID1A in the Cancer Genome Atlas (TCGA) ccRCC Infinium data set. PBRM1, KDM6A, SETD2 and BAP1 were unmethylated in all tumor and normal specimens. KDM5C and ARID1A were unmethylated in the TCGA 219 ccRCC and 119 adjacent normal specimens. Aberrant promoter hypermethylation of PBRM1, BAP1 and the other chromatin-modifying genes examined here is therefore absent or rare in ccRCC.
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Affiliation(s)
- Ilsiya Ibragimova
- Cancer Epigenetics Program and Kidney Keystone Program, Fox Chase Cancer Center, Philadelphia, PA, USA
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19
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Abundance of female-biased and paucity of male-biased somatically expressed genes on the mouse X-chromosome. BMC Genomics 2012; 13:607. [PMID: 23140559 PMCID: PMC3534601 DOI: 10.1186/1471-2164-13-607] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Accepted: 10/08/2012] [Indexed: 11/20/2022] Open
Abstract
Background Empirical evaluations of sexually dimorphic expression of genes on the mammalian X-chromosome are needed to understand the evolutionary forces and the gene-regulatory mechanisms controlling this chromosome. We performed a large-scale sex-bias expression analysis of genes on the X-chromosome in six different somatic tissues from mouse. Results Our results show that the mouse X-chromosome is enriched with female-biased genes and depleted of male-biased genes. This suggests that feminisation as well as de-masculinisation of the X-chromosome has occurred in terms of gene expression in non-reproductive tissues. Several mechanisms may be responsible for the control of female-biased expression on chromosome X, and escape from X-inactivation is a main candidate. We confirmed escape in case of Tmem29 using RNA-FISH analysis. In addition, we identified novel female-biased non-coding transcripts located in the same female-biased cluster as the well-known coding X-inactivation escapee Kdm5c, likely transcribed from the transition-region between active and silenced domains. We also found that previously known escapees only partially explained the overrepresentation of female-biased X-genes, particularly for tissue-specific female-biased genes. Therefore, the gene set we have identified contains tissue-specific escapees and/or genes controlled by other sexually skewed regulatory mechanisms. Analysis of gene age showed that evolutionarily old X-genes (>100 myr, preceding the radiation of placental mammals) are more frequently female-biased than younger genes. Conclusion Altogether, our results have implications for understanding both gene regulation and gene evolution of mammalian X-chromosomes, and suggest that the final result in terms of the X-gene composition (masculinisation versus feminisation) is a compromise between different evolutionary forces acting on reproductive and somatic tissues.
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20
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Berletch JB, Yang F, Xu J, Carrel L, Disteche CM. Genes that escape from X inactivation. Hum Genet 2011; 130:237-45. [PMID: 21614513 PMCID: PMC3136209 DOI: 10.1007/s00439-011-1011-z] [Citation(s) in RCA: 254] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2011] [Accepted: 05/17/2011] [Indexed: 12/30/2022]
Abstract
To achieve a balanced gene expression dosage between males (XY) and females (XX), mammals have evolved a compensatory mechanism to randomly inactivate one of the female X chromosomes. Despite this chromosome-wide silencing, a number of genes escape X inactivation: in women about 15% of X-linked genes are bi-allelically expressed and in mice, about 3%. Expression from the inactive X allele varies from a few percent of that from the active allele to near equal expression. While most genes have a stable inactivation pattern, a subset of genes exhibit tissue-specific differences in escape from X inactivation. Escape genes appear to be protected from the repressive chromatin modifications associated with X inactivation. Differences in the identity and distribution of escape genes between species and tissues suggest a role for these genes in the evolution of sex differences in specific phenotypes. The higher expression of escape genes in females than in males implies that they may have female-specific roles and may be responsible for some of the phenotypes observed in X aneuploidy.
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Affiliation(s)
- Joel B. Berletch
- Department of Pathology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Fan Yang
- Department of Pathology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Jun Xu
- Department of Biomedical Sciences, Tufts University Cummings School of Veterinary Medicine, North Grafton, MA 01536, USA
| | - Laura Carrel
- Department of Biochemistry and Molecular Biology, Pennsylvania State College of Medicine, Hershey, PA 17033, USA
| | - Christine M. Disteche
- Department of Pathology, University of Washington School of Medicine, Seattle, WA 98195, USA. Department of Medicine, University of Washington School of Medicine, Seattle, WA 98195, USA
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21
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Abstract
In humans, sexual dimorphism is associated with the presence of two X chromosomes in the female, whereas males possess only one X and a small and largely degenerate Y chromosome. How do men cope with having only a single X chromosome given that virtually all other chromosomal monosomies are lethal? Ironically, or even typically many might say, women and more generally female mammals contribute most to the job by shutting down one of their two X chromosomes at random. This phenomenon, called X-inactivation, was originally described some 50 years ago by Mary Lyon and has captivated an increasing number of scientists ever since. The fascination arose in part from the realisation that the inactive X corresponded to a dense heterochromatin mass called the “Barr body” whose number varied with the number of Xs within the nucleus and from the many intellectual questions that this raised: How does the cell count the X chromosomes in the nucleus and inactivate all Xs except one? What kind of molecular mechanisms are able to trigger such a profound, chromosome-wide metamorphosis? When is X-inactivation initiated? How is it transmitted to daughter cells and how is it reset during gametogenesis? This review retraces some of the crucial findings, which have led to our current understanding of a biological process that was initially considered as an exception completely distinct from conventional regulatory systems but is now viewed as a paradigm “par excellence” for epigenetic regulation.
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Affiliation(s)
- Céline Morey
- Institut Pasteur, Unité de Génétique Moléculaire Murine, CNRS, URA2578, Paris, France
- * E-mail:
| | - Philip Avner
- Institut Pasteur, Unité de Génétique Moléculaire Murine, CNRS, URA2578, Paris, France
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22
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Lopes AM, Arnold-Croop SE, Amorim A, Carrel L. Clustered transcripts that escape X inactivation at mouse XqD. Mamm Genome 2011; 22:572-82. [PMID: 21769671 DOI: 10.1007/s00335-011-9350-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Accepted: 06/08/2011] [Indexed: 12/19/2022]
Abstract
X Chromosome inactivation (XCI) silences one copy of most X-linked genes in female mammals. Notably, human and mouse differ strikingly in the number and organization of the genes that escape XCI. While on the human X Chromosome (Chr) escape genes are organized in domains, the few known genes that escape inactivation in the mouse appear to be isolated. Here we characterize the gene Cxorf26 and adjacent noncoding transcripts that map to XqD. We assess allelic expression in a nonrandomly X-inactivated cell line and directly demonstrate that 2610029G23Rik (Cxorf26) and its head-to-head neighbor (5530601H04Rik) escape X inactivation, creating a small escape domain. Both genes are robustly expressed from the inactive X Chr at approximately 50 and 30% of the expression levels of the active X, respectively. Additionally, consistent with XCI escape, the first exon of Cxorf26 is embedded within an unmethylated CpG island. To extend these results, we assayed ncRNAs adjacent to three other escape genes, Eif2s3x, Kdm5c, and Ddx3x. By allelic expression, three ncRNAs (D330035k16Rik, D930009k15Rik, and Gm16481) also escape X inactivation in the mouse, consistent with previous studies that reported female-biased expression. Altogether, these results establish that mouse escapees, like their human counterparts, can be clustered. Moreover, the fact that these ncRNAs are not found on the human X raises intriguing questions about potential regulatory roles of rapidly evolving ncRNAs in controlling escape gene expression.
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Affiliation(s)
- Alexandra M Lopes
- Institute of Molecular Pathology and Immunology of the University of Porto, R. Dr. Roberto Frias, S/N, 4200-465 Porto, Portugal.
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23
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Tao KP, Fong SW, Lu Z, Ching YP, Chan KW, Chan SY. TSPYL2 is important for G1 checkpoint maintenance upon DNA damage. PLoS One 2011; 6:e21602. [PMID: 21738728 PMCID: PMC3124543 DOI: 10.1371/journal.pone.0021602] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2010] [Accepted: 06/06/2011] [Indexed: 11/25/2022] Open
Abstract
Nucleosome assembly proteins play important roles in chromatin remodeling, which determines gene expression, cell proliferation and terminal differentiation. Testis specific protein, Y-encoded-like 2 (TSPYL2) is a nucleosome assembly protein expressed in neuronal precursors and mature neurons. Previous studies have shown that TSPYL2 binds cyclin B and inhibits cell proliferation in cultured cells suggesting a role in cell cycle regulation. To investigate the physiological significance of TSPYL2 in the control of cell cycle, we generated mice with targeted disruption of Tspyl2. These mutant mice appear grossly normal, have normal life span and do not exhibit increased tumor incidence. To define the role of TSPYL2 in DNA repair, checkpoint arrest and apoptosis, primary embryonic fibroblasts and thymocytes from Tspyl2 deficient mice were isolated and examined under unperturbed and stressed conditions. We show that mutant fibroblasts are impaired in G1 arrest under the situation of DNA damage induced by gamma irradiation. This is mainly attributed to the defective activation of p21 transcription despite proper p53 protein accumulation, suggesting that TSPYL2 is additionally required for p21 induction. TSPYL2 serves a biological role in maintaining the G1 checkpoint under stress condition.
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Affiliation(s)
- Kin Pong Tao
- Department of Paediatrics and Adolescent Medicine, Center of Reproduction, Development and Growth, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Sze Wan Fong
- Department of Paediatrics and Adolescent Medicine, Center of Reproduction, Development and Growth, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Zhihong Lu
- Department of Paediatrics and Adolescent Medicine, Center of Reproduction, Development and Growth, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Yick Pang Ching
- Department of Anatomy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Kin Wang Chan
- Department of Paediatrics and Adolescent Medicine, Center of Reproduction, Development and Growth, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
| | - Siu Yuen Chan
- Department of Paediatrics and Adolescent Medicine, Center of Reproduction, Development and Growth, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China
- * E-mail:
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Werler S, Poplinski A, Gromoll J, Wistuba J. Expression of selected genes escaping from X inactivation in the 41, XX(Y)* mouse model for Klinefelter's syndrome. Acta Paediatr 2011; 100:885-91. [PMID: 21241365 DOI: 10.1111/j.1651-2227.2010.02112.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIM We hypothesized that patients with Klinefelter's syndrome (KS) not only undergo X inactivation, but also that genes escape from inactivation. Their transcripts would constitute a significant difference, as male metabolism is not adapted to a 'female-like' gene dosage. We evaluated the expression of selected X-linked genes in our 41, XX(Y)* male mice to determine whether these genes escape inactivation and whether tissue-specific differences occur. METHODS Correct X inactivation was identified by Xist expression. Relative expression of X-linked genes was examined in liver, kidney and brain tissue by real-time PCR in adult XX(Y)* and XY* males and XX females. RESULTS Expression of genes known to escape X inactivation was analysed. Relative mRNA levels of Pgk1 (control, X inactivated), and the genes Eif2s3x, Kdm5c, Ddx3x and Kdm6a escaping from X inactivation were quantified from liver, kidney and brain. Pgk1 mRNA expression showed no difference, confirming correct X inactivation. In kidney and liver, XX(Y)* males resembled the female expression pattern in all four candidate genes and were distinguishable from XY* males. Contrastingly, in brain tissue XX(Y)* males expressed all four genes higher than male and female controls. CONCLUSION Altered expression of genes escaping X inactivation probably contributes directly to the XX(Y)* phenotype.
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Affiliation(s)
- Steffi Werler
- Institute of Reproductive and Regenerative Biology, Centre of Reproductive Medicine and Andrology, University Clinics, Muenster, Germany
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25
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Nguyen DK, Yang F, Kaul R, Alkan C, Antonellis A, Friery KF, Zhu B, de Jong PJ, Disteche CM. Clcn4-2 genomic structure differs between the X locus in Mus spretus and the autosomal locus in Mus musculus: AT motif enrichment on the X. Genome Res 2011; 21:402-9. [PMID: 21282478 DOI: 10.1101/gr.108563.110] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In Mus spretus, the chloride channel 4 gene Clcn4-2 is X-linked and dosage compensated by X up-regulation and X inactivation, while in the closely related mouse species Mus musculus, Clcn4-2 has been translocated to chromosome 7. We sequenced Clcn4-2 in M. spretus and identified the breakpoints of the evolutionary translocation in the Mus lineage. Genetic and epigenetic differences were observed between the 5'ends of the autosomal and X-linked loci. Remarkably, Clcn4-2 introns have been truncated on chromosome 7 in M. musculus as compared with the X-linked loci from seven other eutherian mammals. Intron sequences specifically preserved in the X-linked loci were significantly enriched in AT-rich oligomers. Genome-wide analyses showed an overall enrichment in AT motifs unique to the eutherian X (except for genes that escape X inactivation), suggesting a role for these motifs in regulation of the X chromosome.
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Affiliation(s)
- Di Kim Nguyen
- Department of Pathology, University of Washington, Seattle, Washington 98195, USA
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26
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Abstract
A subset of X-linked genes escapes silencing by X inactivation and is expressed from both X chromosomes in mammalian females. Species-specific differences in the identity of these genes have recently been discovered, suggesting a role in the evolution of sex differences. Chromatin analyses have aimed to discover how genes remain expressed within a repressive environment.
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Affiliation(s)
- Joel B Berletch
- Department of Pathology, University of Washington, Seattle, Washington 98195, USA
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27
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Abstract
There is longstanding evidence that X-chromosome inactivation
(XCI) travels less successfully in autosomal than in X-chromosomal chromatin. The interspersed repeat elements LINE1s (L1s) have been suggested as candidates for “boosters” which promote the spread of XCI in the X-chromosome. The present paper reviews the current evidence concerning the possible role of L1s in XCI. Recent evidence, accruing from the human genome sequencing project and other sources, confirms that mammalian X-chromosomes are indeed rich in L1s, except in regions where there are many genes escaping XCI. The density of L1s is the highest in the evolutionarily oldest regions. Recent work on X; autosome translocations in human and mouse suggested failure of stabilization of XCI in autosomal material, so that genes are reactivated, but resistance of autosomal genes to the original silencing is not excluded. The accumulation of L1s on the X-chromosome may have resulted from reduced recombination or late replication. Whether L1s are part of the mechanism of XCI or a
result of it remains enigmatic.
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Affiliation(s)
- Mary F. Lyon
- Mammalian Genetics Unit, Medical Research Council (MRC), Harwell, Oxfordshire OX11 0RD, UK
- *Mary F. Lyon:
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Yang F, Babak T, Shendure J, Disteche CM. Global survey of escape from X inactivation by RNA-sequencing in mouse. Genome Res 2010; 20:614-22. [PMID: 20363980 DOI: 10.1101/gr.103200.109] [Citation(s) in RCA: 278] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
X inactivation equalizes the dosage of gene expression between the sexes, but some genes escape silencing and are thus expressed from both alleles in females. To survey X inactivation and escape in mouse, we performed RNA sequencing in Mus musculus x Mus spretus cells with complete skewing of X inactivation, relying on expression of single nucleotide polymorphisms to discriminate allelic origin. Thirteen of 393 (3.3%) mouse genes had significant expression from the inactive X, including eight novel escape genes. We estimate that mice have significantly fewer escape genes compared with humans. Furthermore, escape genes did not cluster in mouse, unlike the large escape domains in human, suggesting that expression is controlled at the level of individual genes. Our findings are consistent with the striking differences in phenotypes between female mice and women with a single X chromosome--a near normal phenotype in mice versus Turner syndrome and multiple abnormalities in humans. We found that escape genes are marked by the absence of trimethylation at lysine 27 of histone H3, a chromatin modification associated with genes subject to X inactivation. Furthermore, this epigenetic mark is developmentally regulated for some mouse genes.
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Affiliation(s)
- Fan Yang
- Department of Pathology, University of Washington, Seattle, Washington 98195, USA
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Lopes AM, Burgoyne PS, Ojarikre A, Bauer J, Sargent CA, Amorim A, Affara NA. Transcriptional changes in response to X chromosome dosage in the mouse: implications for X inactivation and the molecular basis of Turner Syndrome. BMC Genomics 2010; 11:82. [PMID: 20122165 PMCID: PMC2837040 DOI: 10.1186/1471-2164-11-82] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Accepted: 02/01/2010] [Indexed: 11/12/2022] Open
Abstract
Background X monosomic mice (39,XO) have a remarkably mild phenotype when compared to women with Turner syndrome (45,XO). The generally accepted hypothesis to explain this discrepancy is that the number of genes on the mouse X chromosome which escape X inactivation, and thus are expressed at higher levels in females, is very small. However this hypothesis has never been tested and only a small number of genes have been assayed for their X-inactivation status in the mouse. We performed a global expression analysis in four somatic tissues (brain, liver, kidney and muscle) of adult 40,XX and 39,XO mice using the Illumina Mouse WG-6 v1_1 Expression BeadChip and an extensive validation by quantitative real time PCR, in order to identify which genes are expressed from both X chromosomes. Results We identified several genes on the X chromosome which are overexpressed in XX females, including those previously reported as escaping X inactivation, as well as new candidates. However, the results obtained by microarray and qPCR were not fully concordant, illustrating the difficulty in ascertaining modest fold changes, such as those expected for genes escaping X inactivation. Remarkably, considerable variation was observed between tissues, suggesting that inactivation patterns may be tissue-dependent. Our analysis also exposed several autosomal genes involved in mitochondrial metabolism and in protein translation which are differentially expressed between XX and XO mice, revealing secondary transcriptional changes to the alteration in X chromosome dosage. Conclusions Our results support the prediction that the mouse inactive X chromosome is largely silent, while providing a list of the genes potentially escaping X inactivation in rodents. Although the lower expression of X-linked genes in XO mice may not be relevant in the particular tissues/systems which are affected in human X chromosome monosomy, genes deregulated in XO mice are good candidates for further study in an involvement in Turner Syndrome phenotype.
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Affiliation(s)
- Alexandra M Lopes
- IPATIMUP, Instituto de Patologia e Imunologia Molecular da Universidade do Porto, 4200-465 Porto, Portugal.
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30
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Cantrell MA, Carstens BC, Wichman HA. X chromosome inactivation and Xist evolution in a rodent lacking LINE-1 activity. PLoS One 2009; 4:e6252. [PMID: 19603076 PMCID: PMC2705805 DOI: 10.1371/journal.pone.0006252] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2008] [Accepted: 05/28/2009] [Indexed: 02/05/2023] Open
Abstract
Dosage compensation in eutherian mammals occurs by inactivation of one X chromosome in females. Silencing of that X chromosome is initiated by Xist, a large non-coding RNA, whose coating of the chromosome extends in cis from the X inactivation center. LINE-1 (L1) retrotransposons have been implicated as possible players for propagation of the Xist signal, but it has remained unclear whether they are essential components. We previously identified a group of South American rodents in which L1 retrotransposition ceased over 8 million years ago and have now determined that at least one species of these rodents, Oryzomys palustris, still retains X inactivation. We have also isolated and analyzed the majority of the Xist RNA from O. palustris and a sister species retaining L1 activity, Sigmodon hispidus, to determine if evolution in these sequences has left signatures that might suggest a critical role for L1 elements in Xist function. Comparison of rates of Xist evolution in the two species fails to support L1 involvement, although other explanations are possible. Similarly, comparison of known repeats and potential RNA secondary structures reveals no major differences with the exception of a new repeat in O. palustris that has potential to form new secondary structures.
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Affiliation(s)
- Michael A. Cantrell
- Department of Biological Sciences, University of Idaho, Moscow, Idaho, United States of America
| | - Bryan C. Carstens
- Department of Biological Sciences, University of Idaho, Moscow, Idaho, United States of America
| | - Holly A. Wichman
- Department of Biological Sciences, University of Idaho, Moscow, Idaho, United States of America
- * E-mail:
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31
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Dementyeva EV, Shevchenko AI, Zakian SM. X-chromosome upregulation and inactivation: two sides of the dosage compensation mechanism in mammals. Bioessays 2009; 31:21-8. [PMID: 19153998 DOI: 10.1002/bies.080149] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Mammals have a very complex, tightly controlled, and developmentally regulated process of dosage compensation. One form of the process equalizes expression of the X-linked genes, present as a single copy in males (XY) and as two copies in females (XX), by inactivation of one of the two X-chromosomes in females. The second form of the process leads to balanced expression between the X-linked and autosomal genes by transcriptional upregulation of the active X in males and females. However, not all X-linked genes are absolutely balanced. This review is focused on the recent advances in studying the dosage compensation phenomenon in mammals.
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Affiliation(s)
- Elena V Dementyeva
- Institute of Cytology and Genetics, Russian Academy of Sciences, Siberian Department, Novosibirsk, Russia
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32
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Prothero KE, Stahl JM, Carrel L. Dosage compensation and gene expression on the mammalian X chromosome: one plus one does not always equal two. Chromosome Res 2009; 17:637-48. [PMID: 19802704 PMCID: PMC4941101 DOI: 10.1007/s10577-009-9063-9] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Counting chromosomes is not just simple math. Although normal males and females differ in sex chromosome content (XY vs. XX), X chromosome imbalance is tolerated because dosage compensation mechanisms have evolved to ensure functional equivalence. In mammals this is accomplished by two processes--X chromosome inactivation that silences most genes on one X chromosome in females, leading to functional X monosomy for most genes in both sexes, and X chromosome upregulation that results in increased gene expression on the single active X in males and females, equalizing dosage relative to autosomes. This review focuses on genes on the X chromosome, and how gene content, organization and expression levels can be influenced by these two processes. Special attention is given to genes that are not X inactivated, and are not necessarily fully dosage compensated. These genes that "escape" X inactivation are of medical importance as they explain phenotypes in individuals with sex chromosome aneuploidies and may impact normal traits and disorders that differ between men and women. Moreover, escape genes give insight into how X chromosome inactivation is spread and maintained on the X.
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Affiliation(s)
- Katie E. Prothero
- Department of Biochemistry and Molecular Biology, Penn State College of Medicine, Hershey, PA 17033, USA
| | - Jill M. Stahl
- Department of Biochemistry and Molecular Biology, Penn State College of Medicine, Hershey, PA 17033, USA
| | - Laura Carrel
- Department of Biochemistry and Molecular Biology, Penn State College of Medicine, Hershey, PA 17033, USA
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33
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Escape from X chromosome inactivation is an intrinsic property of the Jarid1c locus. Proc Natl Acad Sci U S A 2008; 105:17055-60. [PMID: 18971342 DOI: 10.1073/pnas.0807765105] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Although most genes on one X chromosome in mammalian females are silenced by X inactivation, some "escape" X inactivation and are expressed from both active and inactive Xs. How these escape genes are transcribed from a largely inactivated chromosome is not fully understood, but underlying genomic sequences are likely involved. We developed a transgene approach to ask whether an escape locus is autonomous or is instead influenced by X chromosome location. Two BACs carrying the mouse Jarid1c gene and adjacent X-inactivated transcripts were randomly integrated into mouse XX embryonic stem cells. Four lines with single-copy, X-linked transgenes were identified, and each was inserted into regions that are normally X-inactivated. As expected for genes that are normally subject to X inactivation, transgene transcripts Tspyl2 and Iqsec2 were X-inactivated. However, allelic expression and RNA/DNA FISH indicate that transgenic Jarid1c escapes X inactivation. Therefore, transgenes at 4 different X locations recapitulate endogenous inactive X expression patterns. We conclude that escape from X inactivation is an intrinsic feature of the Jarid1c locus and functionally delimit this escape domain to the 112-kb maximum overlap of the BACs tested. Additionally, although extensive chromatin differences normally distinguish active and inactive loci, unmodified BACs direct proper inactive X expression patterns, establishing that primary DNA sequence alone, in a chromosome position-independent manner, is sufficient to determine X chromosome inactivation status. This transgene approach will enable further dissection of key elements of escape domains and allow rigorous testing of specific genomic sequences on inactive X expression.
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Nordquist N, Oreland L. RETRACTED ARTICLE: Monoallelic expression of MAO-A in skin fibroblasts. J Neural Transm (Vienna) 2007; 114:713-6. [PMID: 17406964 DOI: 10.1007/s00702-007-0676-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2006] [Accepted: 11/11/2006] [Indexed: 10/23/2022]
Abstract
X chromosome inactivation in mammalian females occurs early in embryonic development and renders most genes on the inactive X chromosome transcriptionally silenced. As a consequence, females will display an X chromosomal parent-of-origin mosaicism with regard to which parental allele that is expressed. Some genes however, escape inactivation and will therefore be expressed from both alleles. In this study we have investigated if the X-linked MAO-A gene have bi- or mono-allelic expression. This information would indicate whether or not MAO-A gene dosage could potentially explain the observed gender differences that show functional connections to the serotonin system, such as aggression and impulsiveness. To investigate the X inactivation status of MAO-A we have used primary clonal cell cultures, on which allelic expression was assessed with RFLP analysis. Our results show that the MAO-A gene has mono-allelic expression in these cells. This could have important implications for understanding traits that display gender differences.
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Affiliation(s)
- N Nordquist
- Department of Neuroscience, Uppsala University, Uppsala, Sweden.
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35
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Chaumeil J, Le Baccon P, Wutz A, Heard E. A novel role for Xist RNA in the formation of a repressive nuclear compartment into which genes are recruited when silenced. Genes Dev 2006; 20:2223-37. [PMID: 16912274 PMCID: PMC1553206 DOI: 10.1101/gad.380906] [Citation(s) in RCA: 372] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
During early mammalian female development, one of the two X chromosomes becomes inactivated. Although X-chromosome coating by Xist RNA is essential for the initiation of X inactivation, little is known about how this signal is transformed into transcriptional silencing. Here we show that exclusion of RNA Polymerase II and transcription factors from the Xist RNA-coated X chromosome represents the earliest event following Xist RNA accumulation described so far in differentiating embryonic stem (ES) cells. Paradoxically, exclusion of the transcription machinery occurs before gene silencing is complete. However, examination of the three-dimensional organization of X-linked genes reveals that, when transcribed, they are always located at the periphery of, or outside, the Xist RNA domain, in contact with the transcription machinery. Upon silencing, genes shift to a more internal location, within the Xist RNA compartment devoid of transcription factors. Surprisingly, the appearance of this compartment is not dependent on the A-repeats of the Xist transcript, which are essential for gene silencing. However, the A-repeats are required for the relocation of genes into the Xist RNA silent domain. We propose that Xist RNA has multiple functions: A-repeat-independent creation of a transcriptionally silent nuclear compartment; and A-repeat-dependent induction of gene repression, which is associated with their translocation into this silent domain.
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Affiliation(s)
- Julie Chaumeil
- Mammalian Developmental Epigenetic Group, UMR 218, Curie Institute, 75248 Paris Cedex 05, France
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36
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Heard E, Disteche CM. Dosage compensation in mammals: fine-tuning the expression of the X chromosome. Genes Dev 2006; 20:1848-67. [PMID: 16847345 DOI: 10.1101/gad.1422906] [Citation(s) in RCA: 377] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Mammalian females have two X chromosomes and males have only one. This has led to the evolution of special mechanisms of dosage compensation. The inactivation of one X chromosome in females equalizes gene expression between the sexes. This process of X-chromosome inactivation (XCI) is a remarkable example of long-range, monoallelic gene silencing and facultative heterochromatin formation, and the questions surrounding it have fascinated biologists for decades. How does the inactivation of more than a thousand genes on one X chromosome take place while the other X chromosome, present in the same nucleus, remains genetically active? What are the underlying mechanisms that trigger the initial differential treatment of the two X chromosomes? How is this differential treatment maintained once it has been established, and how are some genes able to escape the process? Does the mechanism of X inactivation vary between species and even between lineages? In this review, X inactivation is considered in evolutionary terms, and we discuss recent insights into the epigenetic changes and developmental timing of this process. We also review the discovery and possible implications of a second form of dosage compensation in mammals that deals with the unique, potentially haploinsufficient, status of the X chromosome with respect to autosomal gene expression.
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Affiliation(s)
- Edith Heard
- CNRS UMR218, Curie Institute, Paris, France.
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37
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Carrel L, Park C, Tyekucheva S, Dunn J, Chiaromonte F, Makova KD. Genomic environment predicts expression patterns on the human inactive X chromosome. PLoS Genet 2006; 2:e151. [PMID: 17009873 PMCID: PMC1584270 DOI: 10.1371/journal.pgen.0020151] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2006] [Accepted: 08/03/2006] [Indexed: 11/18/2022] Open
Abstract
What genomic landmarks render most genes silent while leaving others expressed on the inactive X chromosome in mammalian females? To date, signals determining expression status of genes on the inactive X remain enigmatic despite the availability of complete genomic sequences. Long interspersed repeats (L1s), particularly abundant on the X, are hypothesized to spread the inactivation signal and are enriched in the vicinity of inactive genes. However, both L1s and inactive genes are also more prevalent in ancient evolutionary strata. Did L1s accumulate there because of their role in inactivation or simply because they spent more time on the rarely recombining X? Here we utilize an experimentally derived inactivation profile of the entire human X chromosome to uncover sequences important for its inactivation, and to predict expression status of individual genes. Focusing on Xp22, where both inactive and active genes reside within evolutionarily young strata, we compare neighborhoods of genes with different inactivation states to identify enriched oligomers. Occurrences of such oligomers are then used as features to train a linear discriminant analysis classifier. Remarkably, expression status is correctly predicted for 84% and 91% of active and inactive genes, respectively, on the entire X, suggesting that oligomers enriched in Xp22 capture most of the genomic signal determining inactivation. To our surprise, the majority of oligomers associated with inactivated genes fall within L1 elements, even though L1 frequency in Xp22 is low. Moreover, these oligomers are enriched in parts of L1 sequences that are usually underrepresented in the genome. Thus, our results strongly support the role of L1s in X inactivation, yet indicate that a chromatin microenvironment composed of multiple genomic sequence elements determines expression status of X chromosome genes.
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Affiliation(s)
- Laura Carrel
- Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
- * To whom correspondence should be addressed. E-mail: (LC); (KDM)
| | - Chungoo Park
- Center for Comparative Genomics and Bioinformatics, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Svitlana Tyekucheva
- Center for Comparative Genomics and Bioinformatics, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Department of Statistics, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - John Dunn
- Department of Pediatrics, Case Western Reserve University School of Medicine, Cleveland, Ohio, United States of America
| | - Francesca Chiaromonte
- Center for Comparative Genomics and Bioinformatics, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Department of Statistics, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Department of Health Evaluation Sciences, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
| | - Kateryna D Makova
- Center for Comparative Genomics and Bioinformatics, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
- * To whom correspondence should be addressed. E-mail: (LC); (KDM)
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38
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Nordquist N, Oreland L. Monoallelic expression of MAOA in skin fibroblasts. Biochem Biophys Res Commun 2006; 348:763-7. [PMID: 16890910 DOI: 10.1016/j.bbrc.2006.07.131] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2006] [Accepted: 07/23/2006] [Indexed: 10/24/2022]
Abstract
X chromosome inactivation in mammalian females occurs early in embryonic development and renders most genes on the inactive X chromosome transcriptionally silenced. As a consequence, females will display an X chromosomal parent-of-origin mosaiscism with regard to which parental allele that is expressed. Some genes, however, escape inactivation and will therefore be expressed from both alleles. In this study, we have investigated if the X-linked MAO-A gene has bi- or mono-allelic expression. This information would indicate whether or not MAO-A gene dosage could potentially explain the observed gender differences that show functional connections to the serotonin system, such as aggression, and impulsiveness. To investigate the X inactivation status of MAO-A we have used primary clonal cell cultures, on which allelic expression was assessed with RFLP analysis. Our results show that the MAO-A gene has mono-allelic expression in these cells. This could have important implications for understanding traits that display gender differences.
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Affiliation(s)
- Niklas Nordquist
- Department of Neuroscience, Uppsala University, Uppsala, Sweden.
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39
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Valley CM, Willard HF. Genomic and epigenomic approaches to the study of X chromosome inactivation. Curr Opin Genet Dev 2006; 16:240-5. [PMID: 16647845 DOI: 10.1016/j.gde.2006.04.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2006] [Accepted: 04/18/2006] [Indexed: 10/24/2022]
Abstract
X chromosome inactivation represents a compelling example of chromosome-wide, long-range epigenetic gene-silencing in mammals. The cis- and trans-acting factors that establish and maintain the patterns and levels of gene expression from the active and inactive X chromosomes remain incompletely understood; however, the availability of the complete genomic sequence of the human X chromosome, together with complementary approaches that explore the computational biology, epigenetic modifications and gene expression-profiling along the chromosome, suggests that the features of the X chromosome that are responsible for its unique forms of gene regulation are increasingly amenable to experimental analysis.
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Affiliation(s)
- Cory M Valley
- Institute for Genome Sciences & Policy, Duke University, 101 Science Drive, CIEMAS 2376, Durham, NC 27708, USA
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Scott LA, Kuroiwa A, Matsuda Y, Wichman HA. X accumulation of LINE-1 retrotransposons in Tokudaia osimensis, a spiny rat with the karyotype XO. Cytogenet Genome Res 2006; 112:261-9. [PMID: 16484782 DOI: 10.1159/000089880] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2005] [Accepted: 07/25/2005] [Indexed: 01/02/2023] Open
Abstract
The observation that LINE-1 transposable elements are enriched on the X in comparison to the autosomes led to the hypothesis that LINE-1s play a role in X chromosome inactivation. If this hypothesis is correct, loss of LINE-1 activity would be expected to result in species extinction or in an alternate pathway of dosage compensation. One such alternative pathway would be to evolve a karyotype that does not require dosage compensation between the sexes. Two of the three extant species of the Ryukyu spiny rat Tokudaia have such a karyotype; both males and females are XO. We asked whether this karyotype arose due to loss of LINE-1 activity and thus the loss of a putative component in the X inactivation pathway. Although XO Tokudaia has no need for dosage compensation, LINE-1s have been recently active in Tokudaia osimensis and show higher density on the lone X than on the autosomes.
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Affiliation(s)
- L A Scott
- Department of Biological Sciences, University of Idaho, Moscow, ID 83844-3051, USA
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Cantrell MA, Ederer MM, Erickson IK, Swier VJ, Baker RJ, Wichman HA. MysTR: an endogenous retrovirus family in mammals that is undergoing recent amplifications to unprecedented copy numbers. J Virol 2006; 79:14698-707. [PMID: 16282470 PMCID: PMC1287555 DOI: 10.1128/jvi.79.23.14698-14707.2005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A large percentage of the repetitive elements in mammalian genomes are retroelements, which have been moved primarily by LINE-1 retrotransposons and endogenous retroviruses. Although LINE-1 elements have remained active throughout the mammalian radiation, specific groups of endogenous retroviruses generally remain active for comparatively shorter periods of time. Identification of an unusual extinction of LINE-1 activity in a group of South American rodents has opened a window for examination of the interplay in mammalian genomes between these ubiquitous retroelements. In the course of a search for any type of repetitive sequences whose copy numbers have substantially changed in Oryzomys palustris, a species that has lost LINE-1 activity, versus Sigmodon hispidus, a closely related species retaining LINE-1 activity, we have identified an endogenous retrovirus family differentially amplified in these two species. Analysis of three full-length, recently transposed copies, called mysTR elements, revealed gag, pro, and pol coding regions containing stop codons which may have accumulated either before or after retrotransposition. Isolation of related sequences in S. hispidus and the LINE-1 active outgroup species, Peromyscus maniculatus, by PCR of a pro-pol region has allowed determination of copy numbers in each species. Unusually high copy numbers of approximately 10,000 in O. palustris versus 1,000 in S. hispidus and 4,500 in the more distantly related P. maniculatus leave open the question of whether there is a connection between endogenous retrovirus activity and LINE-1 inactivity. Nevertheless, these independent expansions of mysTR represent recent amplifications of this endogenous retrovirus family to unprecedented levels.
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Affiliation(s)
- Michael A Cantrell
- Department of Biological Sciences, PO Box 443051, University of Idaho, Moscow, ID 83844, USA.
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Samollow PB. Status and applications of genomic resources for the gray, short-tailed opossum, Monodelphis domestica, an American marsupial model for comparative biology. AUST J ZOOL 2006. [DOI: 10.1071/zo05059] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Owing to its small size, favourable reproductive characteristics, and simple husbandry, the gray, short-tailed opossum, Monodelphis domestica, has become the most widely distributed and intensively utilised laboratory-bred research marsupial in the world today. This article provides an overview of the current state and future projections of genomic resources for this species and discusses the potential impact of this growing resource base on active research areas that use M. domestica as a model system. The resources discussed include: fully arrayed, bacterial artificial chromosome (BAC) libraries; an expanding linkage map; developing full-genome BAC-contig and chromosomal fluorescence in situ hybridisation maps; public websites providing access to the M. domestica whole-genome-shotgun sequence trace database and the whole-genome sequence assembly; and a new project underway to create an expressed-sequence database and microchip expression arrays for functional genomics applications. Major research areas discussed span a variety of genetic, evolutionary, physiologic, reproductive, developmental, and behavioural topics, including: comparative immunogenetics; genomic imprinting; reproductive biology; neurobiology; photobiology and carcinogenesis; genetics of lipoprotein metabolism; developmental and behavioural endocrinology; sexual differentiation and development; embryonic and fetal development; meiotic recombination; genome evolution; molecular evolution and phylogenetics; and more.
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Wen G, Ramser J, Taudien S, Gausmann U, Blechschmidt K, Frankish A, Ashurst J, Meindl A, Platzer M. Validation of mRNA/EST-based gene predictions in human Xp11.4 revealed differences to the organization of the orthologous mouse locus. Mamm Genome 2005; 16:934-41. [PMID: 16341673 DOI: 10.1007/s00335-005-0090-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2005] [Accepted: 08/17/2005] [Indexed: 10/25/2022]
Abstract
Careful manual annotation of the human reference sequence provides a solid basis for the identification of disease-associated genes. Toward this end, we focused on a medically relevant 2.6-Mb region of the human chromosome Xp11.4 between markers DXS9851 and DXS9751 and identified 16 transcription units according to the Vertebrate Genome Annotation (Vega) rules. In order to validate these annotations, we performed a comprehensive RT-PCR expression analysis and a human-mouse comparison. This revealed, despite the high overall genomic conservation of the region, remarkable differences of the gene content between human and mouse. Whereas 12 of 16 annotations were confirmed by RT-PCR in human tissues, for only seven genes mouse orthologs could be identified and found to be expressed. This indicates that a comprehensive and experimentally supported annotation effort of the human genome simultaneously highlights regions with striking differences in gene organization to other species and may indicate evolutionary events specific to the human lineage demanding further functional analyses.
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Affiliation(s)
- Gaiping Wen
- Genome Analysis, Institute of Molecular Biotechnology, Beutenbergstr. 11, 07745, Jena, Germany
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Anderson CL, Brown CJ. Epigenetic predisposition to expression of TIMP1 from the human inactive X chromosome. BMC Genet 2005; 6:48. [PMID: 16194278 PMCID: PMC1262707 DOI: 10.1186/1471-2156-6-48] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2005] [Accepted: 09/29/2005] [Indexed: 12/01/2022] Open
Abstract
Background X inactivation in mammals results in the transcriptional silencing of an X chromosome in females, and this inactive X acquires many of the epigenetic features of silent chromatin. However, not all genes on the inactive X are silenced, and we have examined the TIMP1 gene, which has variable inactivation amongst females. This has allowed us to examine the features permitting expression from the otherwise silent X by comparing inactive X chromosomes with and without TIMP1 expression. Results Expression was generally correlated with euchromatic chromatin features, including DNA hypomethylation, nuclease sensitivity, acetylation of histone H3 and H4 and hypomethylation of H3 at lysines 9 and 27. Demethylation of the TIMP1 gene by 5-azacytidine was able to induce expression from the inactive X chromosome in somatic cell hybrids, and this expression was also accompanied by features of active chromatin. Acetylated histone H3 continued to be observed even when expression was lost in cells that naturally expressed TIMP1; while acetylation was lost upon TIMP1 silencing in cells where expression from the inactive X had been induced by demethylation. Thus ongoing acetylation of inactive X chromosomes does not seem to be simply a 'memory' of expression. Conclusion We propose that acetylation of H3 is an epigenetic mark that predisposes to TIMP1 expression from the inactive X chromosome in some females.
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Affiliation(s)
- Catherine L Anderson
- Department of Medical Genetics, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, CANADA V6T 1Z3
| | - Carolyn J Brown
- Department of Medical Genetics, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, CANADA V6T 1Z3
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Abstract
Mammalian X chromosome inactivation is one of the most striking examples of epigenetic gene regulation. Early in development one of the pair of approximately 160-Mb X chromosomes is chosen to be silenced, and this silencing is then stably inherited through subsequent somatic cell divisions. Recent advances have revealed many of the chromatin changes that underlie this stable silencing of an entire chromosome. The key initiator of these changes is a functional RNA, XIST, which is transcribed from, and associates with, the inactive X chromosome, although the mechanism of association with the inactive X and recruitment of facultative heterochromatin remain to be elucidated. This review describes the unique evolutionary history and resulting genomic structure of the X chromosome as well as the current understanding of the factors and events involved in silencing an X chromosome in mammals.
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Affiliation(s)
- Jennifer C Chow
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
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Yi Y, Mirosevich J, Shyr Y, Matusik R, George AL. Coupled analysis of gene expression and chromosomal location. Genomics 2005; 85:401-12. [PMID: 15718107 DOI: 10.1016/j.ygeno.2004.11.011] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2004] [Accepted: 11/16/2004] [Indexed: 01/05/2023]
Abstract
Microarray technology can be used to assess simultaneously global changes in expression of mRNA or genomic DNA copy number among thousands of genes in different biological states. In many cases, it is desirable to determine if altered patterns of gene expression correlate with chromosomal abnormalities or assess expression of genes that are contiguous in the genome. We describe a method, differential gene locus mapping (DIGMAP), which aligns the known chromosomal location of a gene to its expression value deduced by microarray analysis. The method partitions microarray data into subsets by chromosomal location for each gene interrogated by an array. Microarray data in an individual subset can then be clustered by physical location of genes at a subchromosomal level based upon ordered alignment in genome sequence. A graphical display is generated by representing each genomic locus with a colored cell that quantitatively reflects its differential expression value. The clustered patterns can be viewed and compared based on their expression signatures as defined by differential values between control and experimental samples. In this study, DIGMAP was tested using previously published studies of breast cancer analyzed by comparative genomic hybridization (CGH) and prostate cancer gene expression profiles assessed by cDNA microarray experiments. Analysis of the breast cancer CGH data demonstrated the ability of DIGMAP to deduce gene amplifications and deletions. Application of the DIGMAP method to the prostate data revealed several carcinoma-related loci, including one at 16q13 with marked differential expression encompassing 19 known genes including 9 encoding metallothionein proteins. We conclude that DIGMAP is a powerful computational tool enabling the coupled analysis of microarray data with genome location.
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Affiliation(s)
- Yajun Yi
- Division of Genetic Medicine, Department of Medicine, Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, TX 37232, USA
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Gribnau J, Luikenhuis S, Hochedlinger K, Monkhorst K, Jaenisch R. X chromosome choice occurs independently of asynchronous replication timing. ACTA ACUST UNITED AC 2005; 168:365-73. [PMID: 15668296 PMCID: PMC2171734 DOI: 10.1083/jcb.200405117] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In mammals, dosage compensation is achieved by X chromosome inactivation in female cells. Xist is required and sufficient for X inactivation, and Xist gene deletions result in completely skewed X inactivation. In this work, we analyzed skewing of X inactivation in mice with an Xist deletion encompassing sequence 5 KB upstream of the promoter through exon 3. We found that this mutation results in primary nonrandom X inactivation in which the wild-type X chromosome is always chosen for inactivation. To understand the molecular mechanisms that affect choice, we analyzed the role of replication timing in X inactivation choice. We found that the two Xist alleles and all regions tested on the X chromosome replicate asynchronously before the start of X inactivation. However, analysis of replication timing in cell lines with skewed X inactivation showed no preference for one of the two Xist alleles to replicate early in S-phase before the onset of X inactivation, indicating that asynchronous replication timing does not play a role in skewing of X inactivation.
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Affiliation(s)
- Joost Gribnau
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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Filippova GN, Cheng MK, Moore JM, Truong JP, Hu YJ, Nguyen DK, Tsuchiya KD, Disteche CM. Boundaries between Chromosomal Domains of X Inactivation and Escape Bind CTCF and Lack CpG Methylation during Early Development. Dev Cell 2005; 8:31-42. [PMID: 15669143 DOI: 10.1016/j.devcel.2004.10.018] [Citation(s) in RCA: 172] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Escape from X inactivation results in expression of genes embedded within inactive chromatin, suggesting the existence of boundary elements between domains. We report that the 5' end of Jarid1c, a mouse escape gene adjacent to an inactivated gene, binds CTCF, displays high levels of histone H3 acetylation, and functions as a CTCF-dependent chromatin insulator. CpG island methylation at Jarid1c was very low during development and virtually absent at the CTCF sites, signifying that CTCF may influence DNA methylation and chromatin modifications. CTCF binding sites were also present at the 5' end of two other escape genes, mouse Eif2s3x and human EIF2S3, each adjacent to an inactivated gene, but not at genes embedded within large escape domains. Thus, CTCF was specifically bound to transition regions, suggesting a role in maintaining both X inactivation and escape domains. Furthermore, the evolution of X chromosome domains appears to be associated with repositioning of chromatin boundary elements.
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